High pressure one-way fluid valve mechanism for high speed hydraulic piston pump



. Jan. 2, 1968 J. F. SWIFT 3,361,158

HIGH PRESSURE ONE-WAY FLUID VALVE MECHANISM FOR HIGH SPEED HYDRAULIC PISTON PUMP Filed March 51, 1965 v 5 Sheets-Sheet 1 .X Zak I M C iwi Jan. 2, 1968 J. SWIFT 3,361,158

HIGH PRESSURE ONE-W FLUID VALVE MECHANISM FOR HIGH SPEED HYDRAULIC PISTON PUMP Filed March 31, 1965 3 Sheets-Sheet 2 Tllllllll Jan. 2, 1968 J F SWIFT 3,361,158

HIGH PRESSURE ONE-WIAY FLUID VALVE MECHANISM FOR HIGH SPEED HYDRAULIC PISTON PUMP Filed March 31, 1965 5 Sheets-Sheet 5 0/6 I 54 40 3/ 22 a HIRE] n 3S I: f

* jerzf jzuy HIGH PRESSURE ONE-WAY FLUID VALVE MECHANISM FOR HIGH SPEED HYDRAU- LIC PISTON PUMP John F. Swift, Chicago, 11]., assignor to International Harvester Company, Chicago, Ill., a corporation of Delaware Filed Mar. 31, 1965, Ser. No. 444,365 11 Claims. (Cl. 137-514.3)

ABSTRACT OF THE DISCLOSURE A one-way fluid pressure actuated valve adapted for quiet high-speed operation (e.g. 3000 cycles per minute) at high fluid pressure (e.g. 4500 p.s.i.) characterized by a low-mass movable valve element in cooperation with a pair of opposing adjustable dashpots which eflectively retards, in both directions, the movement of the valve element when it is approaching or nearing the associated stop means. The adjustability of the dashpots by the setting of needle valves permit attuning of the one-way valve pursuant to selected operating parameters.

This invention relates to a one-way fluid pressure actuated valve mechanism. More in particular, this invention relates to construction of hydraulic one-way fluid valves adapted to function efiiciently at high pressure for high speed piston type hydraulic pumps.

A free piston hydraulic pump by its nature has a piston travel or stroke which is variable in position, length, and speed. Consequently, a reciprocating hydraulic piston pump designed to operate as part of a free piston engine, requires a valving means which is independent of any fixed geometry in respect of pump piston stroke or displacement. Such valvin-g means should operate automatically by the rise and fall of hydraulic pressure in the pump chamber. Known valve constructions have been limited to relatively low speeds and low pressures for eflicient operation.

A prime object of the present invention is to provide valve means for a hydraulic piston pump which will operate efliciently at high pump speed and at high pressure.

Another important object of the present invention is to provide valve means according to the preceding object wherein means are provided for adjustably controlling the motion of the valve element so that it accelerates and decelerates smoothly without severe mechanical impact.

A still further object of the present invention is to provide valve means according to the preceding objects which is of low cost and not diflicult to manufacture.

These and other desirable and important objects inherent in the invention will be more readily understood from the ensuing description, the appended claims and the annexed drawings wherein:

FIGURE 1 is a side view partly broken away, showing inlet and outlet valve means according to the present invention assembled within a common or integral housing mounted on the head of a piston hydraulic pump;

FIGURE 2 is a sectional view, partly broken away, taken on line 22 of FIGURE 1 illustrating details of both inlet and outlet valves of the present invention in their closed position;

FIGURE 3 is a sectional view, partly broken away, taken on line 3-3 of FIGURE 1 showing an enlarged detail view of the inlet valve of the present invention;

FIGURE 4 is a sectional view, partly broken away, of the inlet valve of the present invention similar to the upper portion of FIGURE 2 except that the valve is in open position; and

United States Patent FIGURE 5 is a sectional view, partly broken away, of the outlet valve of the present invention, similar to the lower portion of FIGURE 2 except that the valve is in open position.

With a continued reference to the drawings in FIG- URE l the numeral 10 indicates generally inlet and outlet valves according to the present invention assembled as a unitary valve device mounted in rigid relation on the cylinder head 11 of a conventional free piston engine hydraulic pump indicated generally at 12 in FIGURE 1. The free piston engine hydraulic pump 12 may, for example, ibe of the type disclosed in United States Patent No. 3,088,413 issued to A. E. W. Johnson. However, it should be understood that the pump 12 need not be of the free piston engine type but may be in the form of a conventional hydraulic piston type pump. The unitary valve device 10 may be secured to the pump 12 by any conventional means such as by bolts 13.

Referring again to FIGURE 1 the low pressure hydraulic fluid inlet to the unitary valve device 10 is through the inlet pipe 14. As will be apparent later herein the term low pressure referred to herein is usually above atmosphere pressure (e.g. p.s.i.) not only to avoid the occurrence of cavitation in the pump 12 when operating at high speed but also to actuate more rapidly the inlet valve of this invention in one direction. The high pressure hydraulic fluid outlet discharging fluid from the unitary valve device 10 is through the outlet pipe 15. Thus the inlet pipe 14 draws fluid at low pressure from a source (not shown) and the outlet pipe 15 discharges the pumped fluid which pipe leads to a high pressure fluid receiver such as a hydraulic motor (not shown).

Pipe 16 in FIGURE 1 is always in communication with the low pressure inlet pipe 14 by an internal passage (not shown) disposed in the unitary valve device 10 and may be connected for communication with a conventional low pressure accumulator (not shown). Pipe 17 in FIG- URE 1 is always in communication with the high pressure outlet pipe 15 by another internal passage (not shown) disposed in the unitary valve device 10 and may be connected for communication with a high pressure accumulator. Thus it will be apparent that fluid flows in both directions through the pipes 16 and 17. However, it should be understood that one or both of the pipes 16, 17 may be capped and thus not employed as will be apparent from a further understanding of the valve means disposed in the unitary valve device 10 now to be described.

Referring now to FIGURE 2 it will be seen that the unitary valve device 10 includes an inlet one-way fluid valve mechanism indicated generally by the numeral 18 and an outlet one-way fluid valve mechanism indicated generally by the numeral 19. The construction and the novel features of the valves 18 and 19 are the essence of the present invention. The inlet valve 18 will now be described.

The inlet valve 18 includes a housing 20 and it will be noted from FIGURE 2 that the housing for both valves 18 and 19 may comprise a single casting as shown, but obviously can be divided from housing 20a of the outlet valve 19. The housing 20, 20a as shown in the drawings of the preferred embodiment of the invention includes a pump manifold section 20x. The pump manifold section 20x is provided with a bore forming an unrestricted passage 21 leading directly to the cylinder head 11 of the pump 12. Thus on the pumping stroke of the piston in the hydraulic pump 12 fluid flows out of the passage 21 toward the outlet valve 19 and on the intake stroke of the piston in the hydraulic pump 12 fluid flows into the passage 21 from the inlet valve 18.

The housing 20 for the inlet valve 18 is provided with a longitudinal bore 22 which is closed on both ends sealingly by threaded plugs 23 and 24. Abutting the inner surface of the plug 23 and extending longitdinally therefrom is a stationary valve member generally indicated at 25. The stationary valve member 25 includes a flange portion 26 which seats on shoulder 27 formed by enlarged bore 28 and the bore 22 as best seen in FIGURE 3. Thus it will be apparent that by removing the threaded plug 23 the stationary valve member 25 may conveniently be removed from the housing 20.

Referring again to FIGURE 3 it will be seen that i the stationary valve member 25 includes a shank portion 29 extending longitudinally as shown. Disposed in the longitudinal bore 22 is a movable valve plunger indicated generally by the numeral 30 which is slidable in the longitudinal direction with respect to the inner end portion of the shank 29. The plunger 30 is provided with a circumferential groove 31 which groove is registerable with annular groove 32 in the housing 20 and in continuousregistration with annular groove 33 also disposed in the housing 20. It will be noted that the construction of the valve plunger 30 is such that its mass is as low as practical and. thus its inertia mass is minimized. The valve plunger 30 is thus provided with hollow portions 34- and 35 which are utilized as described later herein.

In FIGURE 3 it will be seen that the plunger 30 is provided with a circular bore 36 which slides longitudinally on the inner end section 37 of the shank 29 having a reduced diameter. Thus it will be apparent that the valve plunger 30 is movable leftwardly along the inner end section 37 of the shank 29 limited by the stop formed by the shoulder 38.

Referring again to FIGURE 3 it will be seen that the inner end portion of the stationary valve member 25 includes an open end bore 39 forming a variable volume compartment 40 with the hollow portion 34 of the plunger 30. Disposed in the bore 39 is a conventional check valve ball 41 urged into seating relation by. the small compression spring 42. The inlet for the check valve 41, 42 is a duct 43 in the stationary valve member 25 communicating with the annular space or chamber 44 formed by the shank 29 and bore 22. The duct 43 is also provided with an adjustable fluid flowrestriction in the form of a conventional needle valve 45. Thus fluid flow through the duct 43 may be adjustably set in accordance with operating parameters of the inlet valve 18.

From FIGURE 3 it will also be observed that the open end bore 39 includes a channel 46 which also leads to the annular space 44 independently of the check valve 41, 42. However, as in the case of duct 43, the channel 46 is also provided with an adjustable fluid flow restriction in the form of another conventional needle valve 47. Thus fluid flow through the channel 46 may be adjustably set in accordance with operating parameters of the inlet valve 18.

From the foregoing it will be apparent that fluid pressure in the annular space 44 exerts a piston action on the annular face 48 of the plunger 30 and also fluid pressure in the compartment 40 exerts a piston action on the plunger 30. Thus it may be said that the plunger 30 is a piston in relation to the stationary valve member 25 and the bore 22. It will be observed that the stationary valve member 25 is provided with a plurality of small radial ports 49 communicating the annular space 44 with compartment 40. However, it will also be observed that as the movable valve plunger 30 moves leftwardly the cylindrical bore 36 thereof closes fluid communication of the radial ports 49. The compression spring 50 urges the plunger 30 toward the closed position of the inlet valve 30 as shown in FIGURE 3.

Referring now to FIGURES 2 and 3 it will be seen that abutting the plug 24 and extending inwardly of the inlet valve 18 is another stationary valve member indicated generally by the numeral 51 and is constructed identical with the above described stationary valve member 25. Accordingly the elements of valve member 51 corresponding to the elements of the valve member 25 bear the same numerical designations except primed unless otherwise indicated.

The cylindrical bore 52 on the rightward end portion of the movable valve member 30 fits slidably over the inner end section 37'. of the stationary valve member 51 similarly to that described for the valve member 25.

In FIGURE 2 it will be apparent that the outlet valve 19 is constructed substantially identical with that of the inlet valve 18 above described except as hereinafter mentioned. Accordingly the elements of the outlet valve 19 corresponding to similar elements of the inlet valve 18 will be corresponding numerical designations except the subscript letter a is added thereto. The operation of the valves 18 and 19 will now be described. I

The piston of the pump 12 in FIGURE 1 will be assumed to have just completed its pumping stroke and therefore the start of its cycle is that the pump piston is about to commence its retractive or fluid intake stroke. At this time the movable valve plunger 30 and 30a of the inlet valve 18 and outlet valve 19, respectively will be in closed position as shown in FIGURES 2 and 3. Now as the pump piston of the pump 12 commences to move on its intake stroke the fluid pressure in the passage 21 decreases thus creating a fluid pressure differential between the outlet passage 53 and the inlet passage 54 of the valve mechanism 18. The greater fluid pressure of this fluid pressure differential acts upon the valve plunger 30 urging it leftwardly toward open position. It will thus be apparent that the characteristics of the spring 50 bears upon the pressure differential required of the inlet pressure passage 54 over the outlet passage 53 to actuate the valve plunger 30 to open position. When this fluid pressure differential is of a magnitude sufldcient to overcome the spring 50 the valve plunger 30 begins to move leftwardly toward open position. As soon as the circumferential groove 31 of the valve plunger 30 moves sufficiently to register with the annular groove 32 in the housing 20 fluid communication between the inlet passage 54 and the outlet passage 53 is established and thus fluid at low pressure from the inlet pipe 14 enters the pumping chamber of the pump 12 through passage 21.

Now as the valve plunger 30 moves leftwardly fluid from the inlet passage 54 enters the volume expanding compartment 40' through channel 46 and also through the duct 43' by unseating the check valve ball 41'. Thus fluid from the inlet passage 54 enters the compartment 40 at a rate sufliciently high to avoid cavitation. Mean while fluid in the volume diminishing compartment 40 discharges into the outlet passage 53 through channel 46 and, during initial leftward movement of the valve plunger 30, the ports 49. During this initial stage of leftward movement of the valve plunger 3% the rate of motion of the valve plunger 36 is governed by the rate at which the volume of compartment 46 diminishes through discharge of fluid therein as controlled by the aggregate cross-sectional area of the ports 49 and the effective crosssectional area of the channel 46 as restricted by the needle valve 47 for no fluid discharges from the compartment 40 through the duct 43 as the ball check valve 41 is seated. Thus the rate of motion during the initial movement of the valve plunger 30 may be as high as desired by appropriately choosing the number of radial ports 49 and their cross-sectional area.

When the valve plunger 31 has moved leftward sufficiently to close ports 49 thereby terminating communica tion therethrough between compartment 40 and outlet passage 53 the rate of further reduction of the volume of compartment 40 is further lowered because all fluid discharged from compartment 40 is limited by the flow through channel 46. Thus the restriction of fluid flow through channel 46 is important for it profoundly affects the rate of movement of the valve plunger 30 leftwardly after the ports 49 are closed and the annular face 48 of the valve plunger 30 approaches proximate the limit or stop provided by the shoulder 38. From this it will be apparent that the arrangement above described functions as a shock absorber or dashpot means which prevents severe impact of the valve plunger 30 against the stop or shoulder 38. At this point the valve plunger 30 will have moved leftwardly but not necessarily to its extreme leftward limit shown in FIGURE 4. The inlet mechanism 18 thus remains open approximately in the position as shown in FIGURE 4 until the piston of the pump 12 completes its intake stroke at which time the pressure differential between the intake passage 54 and the outlet passage 53 of the valve mechanism 18 becomes less than that required by the urging of the spring 50 and thus the valve plunger 30 commence-s rightward movement toward the closed position shown in FIGURES 2 and 3.

Initial rightward movement of the valve plunger 30 from the position shown in FIGURE 4 begins to diminish the volume of compartment 40' by discharging fluid therefrom to inlet passage 54 through channel 46 and ports 49' only as the duct'43' is closed by seating of the check valve ball 41. Hence the initial rightward movement of the valve plunger 30 will be at a high rate until the ports 49 are closed. Further rightward movement of the valve plunger 30 is sharply retarded for the discharge of fluid from compartment 40 is limited by channel 46 and the fluid flow restriction imposed by the needle valve 47'. Here again it will be apparent that the arrangement above described functions as a shock absorber or dashpot means which prevents severe impact of the valve plunger 30 against the stop or shoulder 38'. Meanwhile the volume of compartment 40 is expanding but fluid from the outlet passage 53 enters the compartment 40 through channel 46 and duct 43 for the check valve ball 41 unseats. Thus the valve plunger 30 moves to the position illustrated in FIGURES 2 and 3 whereby fluid communication between the inlet passage 54 and the outlet passage 53 is closed.

Now it will be appreciated by those skilled in the art that if the piston of the pump 12 commences its pumping stroke and the valve mechanism 18 is not completely closed at least some fluid would move from the outlet passage 53 to the inlet passage 54 which obviously would decrease the efficiency of the pump 12 and particularly when the pump 12 is operating at high speed and at high hydraulic pressure such losses would be seriously high. In the present invention if the cyclic speed of the pump 12 is so high that the force of the spring 50 is per se insuflicient to close the valve mechanism 18 before the piston of the pump 12 commences its pumping stroke, then the fluid pressure created by the commencement of the pumping stroke is utilized to act in piston-like manner on the annular face 48 of the valve plunger 30 as well as entering compartment 40. Thus the force of the spring 50 is augmented by high fluid pressure in the outlet passage 53 occurring during the pumping stroke of the pump 12. Therefore the valve mechanism 18 closes promptly at high pump speeds efficiently.

Where the pump 12 is operating at high speeds such as that of a 'free piston engine hydraulic pump it is necessary that the source of low pressure fluid supplied to the inlet passage 54 be at super-atmospheric pressure and the characteristics of the spring 50 should be appropriaately chosen accordingly.

The outlet valve mechanism 19, except as mentioned, is constructed substantially the same and operates similar to the inlet valve mechanism 18 above described. However it may be advisable to employ a spring 50a having different characteristics than the spring 50. In this respect it will be noted that the fluid pressure in the outlet passage 53a of outlet valve mechanism 19 during operation is of a higher order than that for the inlet side of the valve mechanism 18.

The needle valves 45 and 45' of the inlet valve mech anism 18 and the needle valves 45a and 45a of outlet valve mechanism 19 are set to avoid cavitation of fluid during expansion of their respectively associated compartments. The needle valves 47 and 47 of the inlet valve mechanism 18 and the needle valves 47a and 47a of the outlet valve mechanism 19 are set to retard sufliciently the rate of movement of the respective valve plungers toward their respective stop means when the valve plungers reach positions proximate the stop means. Particularly when the pump 12 is operating at high output pressure the proper setting of the needle valves 47, 47, 47a and 47a prevents noise and damage arising from impact by the valve plungers against their associated stop means.

From the above it will be apparent that the adjustability of the needle valves provides means for attuning each valve mechanism in accordance with operating parameters of the hydraulic system to which the valve mechanisms of this invention are employed or utilized. Such parameters may include fluid viscosity, operating temperature, and speed of the hydraulic pump. For example, a unitary valve device 10 having an inlet valve mechanism 18 and an outlet valve mechanism 19 constructed substantially in accordance with the embodiment of the invention disclosed herein operated quietly and efficiently in a hydraulic system wherein the hydraulic pump, such as the pump 12, operated at a speed of 3000 cycles per minute at a mean output fluid pressure of 4500 psi.

Having now described a preferred embodiment of the invention it can now be seen that the objects of the invention have been fully achieved and it must be understood that changes and modifications may be made which do not depart from the spirit of the invention as disclosed nor from the scope thereof as defined in the appended claims.

What is claimed is:

1. A one-way fluid pressure actuated valve mechanism comprising a housing having a longitudinal bore disposed therein, an inlet passage and an outlet passage disposed in said housing communicatively connected with said bore, a fluid pressure actuated valve plunger slidably disposed for axial movement in said bore, said valve plunger being axially movable in one direction toward a first stop means for communicatively connecting for fluid flow said inlet passage with said outlet passage when the fluid pressure in said inlet passage exceeds the fluid pressure in said out let passage, said valve plunger being axially movable in the other direction toward a second stop means for terminating fluid flow communication between said inlet passage and said outlet passage when the fluid pressure in said outlet passage exceeds the fluid pressure in said inlet passage, and adjustable dashpot means disposed in said housing for retarding the rate of movement of said valve plunger during at least a portion of its movement proximate to each of said stop means for substantially reducing the severity of mechanical impact of said valve plunger against said stop means, said dashpot means being adjustable for controllably retarding the rate of move. ment of said valve plunger whereby said mechanism may be operably attuned in accordance with selected operating parameters.

2. A one-way fluid pressure actuated valve mechanism comprising -a housing having a longitudinal bore therein, inlet and outlet passages in said housing communicatively connected with said bore, an axially movable valve plunger slidably disposed in said bore, said valve plunger being fluid pressure actuated in one direction toward a first stop means for communicating said inlet passage with said outlet passage when the fluid pressure in said inlet passage exceeds the fluid pressure in said outlet passage by a predetermined fluid pressure diiferenti-al, said valve plunger being actuated in the opposite direction toward a second stop means for terminating communication between said inlet passage and said outlet passage when the fluid pressure in said outlet passage plus said predetermined fluid pressure dilferential combinedly exceeds the fluid pressure in said inlet passage, a first dashpot positioned to retard the rate of movement of said valve plunger during at least 'a portion of its move ment in said one direction, and a second dashpot positioned to retard the rate of movement of said valve plunger'during at least a portion of its movement in said opposite direction, said first dashpot includes a variable volume first compartment and said second dashpot includes a variable volume second compartment, the volume of each of said compartments being varied in correspond ing relation with the position of said movable valve plunger, a first fluid flow channel communicatively connecting said first compartment with said outlet passage for fluid flow therethrough in both directions and a second fluid flow channel communicativelyconnecting said second compartment with said'inlet passage for fluid flow therethrough in both directions whereby fluid is discharged from said firstcompartment'against fluid pressure in said outlet pass age when said valve plunger moves in one direction and fluid is discharged from said second compartment against fluid pressure in said inlet passage when said valve plunger moves in the opposite direction thereby retarding the rate of movement of said valve plunger in both directions for presenting said valve plunger from contacting said stop means at high velocity.

3. A one-way fluid pressure actuated valve mechanism according to claim 2 wherein primary fluid flow restrictive means are disposed in said housing for adjustably controlling the rate of fluid flow through at least one of said channels for attuning the operation of said valve mechanism in accordance with selected operating parameters.

4. A one-way fluid pressure actuated valve mechanism according to claim 3 wherein said primary fluid flow restrictive means comprises at least one adjustable needle valve. I p 1 5. A one-Way fluid pressure actuated valve mechanism according to claim 2 wherein at least one of said dashpots includes port means communicatively connecting at least one of said compartments with one of said passages positioned for closing by 'said valve plunger when said valve plunger moves proximate to at least one of said stop means whereby during further movement of said valve plunger toward said stop means fluid discharge from said compartment is limited to fluid flow through one of said channels thereby further retarding the rate of movement of said valve plunger toward said one of said stop means.

6. A one-way fluid pressure actuated valve mechanism according to claim 2 wherein said first dashpot includes first port means communicatively connecting said first compartment with said outlet passage positioned for closing by said valve plunger when said valve plunger moves in one direction proximate to said first stop means thereby further retarding the rate of movement of said valve plunger toward said first stop means by'limiting fluid discharge from said first compartment to fluid flow through said first channel, and said second dashpost includes'second portrneans communicatively connecting said second compartment with said inlet passage positioned for closing by said valve plunger when said valve plunger moves in the opposite direction proximate to said second stop means thereby further retarding the rate of movement of said valve plunger toward said second stop means by limiting fluid discharge from said second compartment to fluid flow through said second channel.

7. A one-way fluid pressure actuated valve mechanism comprising a housing having a longitudinal bore therein, inlet and outlet passages in said housing communicatively connected with said bore, an axially movable valve plunger slidably disposed in said bore, said valve plunger being fluid pressure actuated in one direction toward a first stop means'for communicating said inlet passage with saidoutlet passage when the fluid pressure in said inlet passage exceeds the fluid pressure in said outlet passage by a predetermined fluid pressure differential, said valve plunger being actuated in the opposite direction toward a second stop means for terminating communica- 8 tion between said inlet passage and said outlet passage when the fluid pressure in said outlet passage plus said predetermined fluid pressure differential combinedly exceeds the fluid pressure in said inlet passage, a first dash post positioned to retard the rate of movement of said valve plunger during at least a portion of its movement in said one direction, and a second dashpot positioned to retard the rate of movement of said valve plunger during at least a portion of its movement in said opposite direction, said first dashpot includes a variable volume first compartment and said second dashpot includes a variable volume second compartment, the volume of each of said compartments being varied in corresponding relation with the position of said movable valve plunger, a first fluid flow channel communicatively connecting said first compartment with said outlet passage for fluid flow therethrough in both directions for discharging fluid from said first compartment against fluid pressure in said outlet passage when said valve plunger moves in one direction to retard the rate of movement of said valve plunger in said one direction, a second fluid flow channel communicatively connecting said second compartment with said inlet passage for fluid flow therethrough in both directions for discharging fluid from said second compartment against fluid pressure in said inlet passage when said valve plunger moves in the opposite direction to retard the rate of movement of said valve plunger in said 0pposite direction, a first auxiliary fluid flow duct communicativelyconnecting said first compartment with said outlet passage for fluid flow therethrough and a second auxiliary fluid flow duct communicatively connecting said second compartment with said inlet passage for fluid flow therethrough, and check valve means positioned to permit fluid flow in said ducts only in the direction to enter said compartments thereby eliminating fluid cavitation in said compartments.

8. A one-way fluid pressure actuated valve mechanism according to claim 7 wherein primary fluid flow adjustable restrictive means are disposed in said housing for adjustably controlling the rate of fluid flow through at least one of said channels, and secondary fluid flow adjustable restrictive means are disposed in said housing for adjust-ably controlling the rate of fluid flow through at least one of said ducts for attuning the operation of said valve mechanism in accordance with selected operatin g parameters.

9. A one-way fluid pressure actuated valve mechanism according to claim 8 wherein said primary and secondary fluid flow restrictive means comprises adjustable needle valves. p

10. A one-way fluid pressure actuated valve mechanism according to claim 7 wherein at least one of said dashpots includes port means communicativelyconnecting at least one of said comparments with one of said passages positioned for closing by said valve plunger when said valve plunger moves proximate to at least one of said stop means whereby during further movement of said valve plunger toward said stop means, fluid discharge from said compartment is limited to fluid flow through one of said channels thereby further retarding the rate of movement of asid valve plunger toward said stop means.

' 11. A one-way fluid pressure actuated valve mechanism according to claim 7 wherein said first dashpot includes first port means communicatively connecting said first compartment with said outlet passage positioned for closing by said valve plunger when said valve plunger moves in one direction proximate to said first stop means thereby further retarding the rate of movement of said valve plunger toward said first stop means by limiting fluid dis-' charge from said first compartment to fluid flow through said first channel, and said second dashpot includessec- 0nd port means communioatively onnecting said second compartment with said inlet passage positioned for closing by said valve plunger when said valve plunger moves in the opposite direction proximate to said second stop 2,421,810 6/1947 Simpson 251-51 means thereby further retarding the rate of movement 2,667,893 2/1954 Kupiec 137-514 of said valve plunger toward said second stop means by 2,920,645 1/1960 Younghaus 137496 limiting fluid discharge from said second compartment to fluid flow through said second channel. 5 FOREIGN PATENTS References Cited 227,046 9/1962 Austrla.

UNITED STATES PATENTS WILLIAM F. ODEA, Primary Examiner.

1,010,206 11/ 1911 Wainwright 137--5 14.3 W, H, WRIGHT, Assistant Examiner. 

